Principles of Engineering Final Exam Review

Engineering

profession in which knowledge of advanced mathematical and natural sciences gained by higher education, experience, and practice; is devoted to creation of new technology for benefit of humanity.

Engineering Technology

profession in which knowledge of applied mathematical and natural sciences gained by higher education, experience, and practice; devoted to application of engineering principles and implementation of technological advances for benefit of humanity. Education focuses on analyzing, applying, implementing and improving existing technologies.

IMA

Distance effort moves / distance load moves

AMA

Load / Effort

Efficiency

AMA / IMA x 100% Nothing in the real world is more than 100% efficient.

Class 1 Lever

fulcrum in middle,

Class 2 Lever

load in middle

Class 3 Lever

effort in middle

IMA of a lever

Length of effort arm/ length of load arm

IMA of a wheel and axle

radius of effort arm/ radius of load arm

IMA of a screw

circumference / pitch of screw (inches per thread) = πd/P

IMA of an inclined plane

Length of sloped side of ramp/ height of ramp

IMA of a wedge

Length of sloped side of wedge/ width of wedge

IMA of a pulley

Number of strands supporting load.

Compound Machines

MAtotal = MA1 X MA2

Work

Force · Distance (parallel)

Gears, sprockets and drive pulleys

Transform rotational energy by changing position, rotational directions, speed and torque.

n

number of teeth

d

diameter

w

rotational speed (rpm)

t

torque (in lbs or Nm)

driver

Causes motion (in)

idler gear

allows the driver and driven gears to rotate in the same direction.

compound gear train

Break down into simple gear trains and multiply individual Gear Ratios.

sprockets

use chains: noisier, more expensive, stronger, need lubrication

driver pulleys

use belts: quieter, cheaper, weaker, no lubrication

nonrenewable

can be used up; oil, coal, uranium.

renewable

more can be made; bio fuels, plants, animals

inexhaustible

we don't do anything to make more; solar, wind, hydro- electric

work

Force x distance(parallel) (Joules)

mechanical power

Work/Time (Watts)

electrical power

P=IV (Watts)

voltag

Set up circuit, measure across component.

current

Multimeter bridges circuit; current must go through multimeter.

resistance

Remove component from circuit, measure across component.

voltage(formula)

(abb. V or E) - units are volts (V): Electromotive force: pressure or force of electricity

current(formula)

(abb. I) - units are amps (A) flow of electrons

resistance(formula)

(abb. R) - units are Ohms (Ω): resistance to current flow

ohms law

V = I * R

power

P = V * I

series resistors

One path for current: Rtotal = R1+R2

parallel resistors

Multiple paths for current: 1/Rtotal = 1/R1+1/R2

hydrogen fuel

Hydrogen fuel cells combine hydrogen and oxygen to create electricity; create no pollution, only water. An emerging technology with many issues such as storage and distribution.

thermodynamics

study of effects of work, heat flow, and energy on a system

Matter is made up of molecules in motion (kinetic energy), an increase in temperature increases motion

absolute zero

occurs when all kinetic energy is removed from a object 0 K = -273° C

zeroth law of thermodynamics

If two systems are separately found to be in thermal equilibrium with a third system, first two systems are in thermal equilibrium with each other.

1st law of thermodynamics

Energy cannot be created or destroyed.

2nd law of thermodynamics

thermal energy moves from hot to cold. Entropy always increases.

entropy

(measure of disorder of energy)

convection

transfer of heat through (moving fluid)

conduction

transfer of heat through touching objects

radiation

transfer of heat through electromagnetic waves through space or air

rate of transfer

P= A∆T/r-value = kA *∆T / L where r-value is thermal resistance, T is temperature, A is area, L is length and k is thermal conductivity.

heat energy transfer

Q= m * Cp*∆T where Cp is specific heat capacity of a material and m is mass of object

multiple layers of insulation

Add r-values of multiple layers to get total r-value. Design, construct, and test recyclable insulation materials.

statics

used to mathematically analyze forces on a structure.

Newton's 1st law of motion (law of inertia)

An object in a state of rest or

uniform motion will continue to be so unless acted upon by another force.

newton's 2nd law of motion

acceleration of an object is proportional to

net force acting on object and inversely proportional to object's mass.

(F=MA)

newton's third law of motion

For every action force, there is an equal and

opposite reaction force.

static equilibrium

No net external forces acting upon a particle or rigid body;

body remains at rest or continues at constant velocity.

Σ Moments (about a point) = 0; Σ Forces in x = 0; Σ Forces in y = 0

moment

rotational forces acting on an object = Force * perpendicular distance.

centroid

center of mass of an object and can be calculated from its dimensions.

rectangle

x = x(max) / 2

y = y(max) / 2

triangle

x = x(max) / 3

y = y(max) / 3

semi-circle

x = radius

y = 4r / (3pi)

centroid of compound shapes

x = Σ (xi * Ai) / Σ xi, where xi is centroid of each

shape and Ai is area of each shape.

moment of inertia

describes stiffness of a beam due to its cross section

I = bh3/12 for a rectangular cross section with height of h and width of b

max deflection

describes how much it can bend ∆max= FL3 / (48 E I) where F is

applied force, L is length, I is moment of inertia and E is modulus of elasticity, a property of material

free body diagrams

illustrate forces acting upon a given body including applied and reaction and are a necessary step in solving for static equilibrium.

normal force

a reaction force perpendicular to surface the object touches.

vector quantities

have both magnitude and direction and trigonometry can be

used to break them down into x and y components. Fx = F * cos(θ); Fy = F * sin(θ); θ = tan-1(Fy/Fx)

resultant

one vector, which has the same effect on a body as two or more vectors that are actually acting on that body.

solving for static equilibrium

1. Assume body is rigid.

2. Choose a rotational point (with most unknowns go

through it) and solve for Σ M = 0

3. Then solve for Σ Fx = 0, and Σ Fy = 0

materials

are substances with which all objects are made, each with its own physical and chemical properties.

elements

one type of atom - cannot be broken down

compounds

multiple elements chemically bonded.

mixtures

multiple elements or compounds not chemically bonded.

material classification

metallic, ceramic, organic, polymeric, and composite.

recycling

an important consideration when choosing materials.

material selection

based upon mechanical, thermal, electromagnetic, and chemical properties as well as cost.

manufacturing process

A sequence of operations and processes designed to create a specific product.

tensile stress test

Measures the deformation and breaking point of a test sample under static tensile force.

hardness test

Brinell or Rockwell hardness measures a material's resistance to a probe creating a crater in it.